Method for measuring scanning pattern of optical scanning apparatus, apparatus for measuring scanning pattern, and method for calibrating image

ABSTRACT

An apparatus for measuring a scanning pattern of an optical scanning apparatus can easily reduce the effect of stray light and improve the measurement accuracy of the scanning pattern. An apparatus for measuring a scanning pattern of an optical scanning apparatus ( 100 ), which scans an object being illuminated with illumination light and generates a display image of the object being illuminated, includes a screen ( 11 ) scanned by the illumination light and an optical position detector ( 12 ) that detects the position of an irradiation spot of the illumination light on the screen ( 11 ). The apparatus for measuring a scanning pattern sequentially detects a position of the irradiation spot at predetermined time points with the optical position detector ( 12 ) during scanning of the screen ( 11 ) to measure the scanning pattern of the illumination light.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Continuing Application based onInternational Application PCT/JP2015/001701 filed on Mar. 25, 2015, thecontent of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a method for measuring a scanning pattern ofan optical scanning apparatus, an apparatus for measuring a scanningpattern, and a method for calibrating an image.

BACKGROUND

A known example of an optical scanning apparatus scans an object beingilluminated by irradiating the object being illuminated withillumination light from an optical fiber through an illumination opticalsystem. The scanning endoscope apparatus scans while displacing theemission end of the optical fiber with an actuator and deflecting theillumination light, detects backscattered light from the object beingilluminated, and generates an image (for example, see JP 5190267 B2 (PTL1)).

Before scanning a target area of the object being illuminated, theoptical scanning apparatus disclosed in PTL 1 directly scans an opticalposition detector provided with a coordinate information acquisitionfunction, such as a Position Sensitive Detector (PSD), with illuminationlight and acquires the scanning pattern of the illumination light.During scanning of a target area of the object being illuminated, theoptical scanning apparatus uses the scanning pattern, acquired inadvance, to calibrate the pixel positions in the image of the objectbeing illuminated obtained by scanning the object being illuminated andgenerates a display image.

CITATION LIST Patent Literature

PTL 1: JP 5190267 B2

SUMMARY

One aspect of this disclosure is directed to a method for measuring ascanning pattern of an optical scanning apparatus that scans an objectbeing illuminated with illumination light and generates a display imageof the object being illuminated, the method comprising:

-   -   scanning a screen with the illumination light; and    -   acquiring irradiation position information by sequentially        detecting, with an optical position detector, a position of an        irradiation spot of the illumination light on the screen at a        predetermined plurality of time points during scanning of the        screen.

Another aspect of this disclosure is directed to an apparatus formeasuring a scanning pattern of an optical scanning apparatus that scansan object being illuminated with illumination light and generates adisplay image of the object being illuminated, the apparatus formeasuring a scanning pattern comprising:

-   -   a screen scanned by the illumination light; and    -   an optical position detector configured to detect a position of        an irradiation spot of the illumination light on the screen,        wherein    -   the apparatus for measuring a scanning pattern sequentially        detects the position of the irradiation spot at a predetermined        plurality of time points with the optical position detector        during scanning of the screen to measure the scanning pattern of        the illumination light.

The screen may have a thickness equal to or less than a diameter of theirradiation spot.

The apparatus for measuring a scanning pattern of an optical scanningapparatus may further comprise a projection optical system configured toproject the irradiation spot on the screen onto the optical positiondetector.

When the apparatus comprises the projection optical system, at least oneof a first condition, a second condition, and a third condition ispreferably satisfied,

-   -   the first condition being that the screen has a thickness equal        to or less than a diameter of the irradiation spot,    -   the second condition being that a diffusion angle of the        illumination light by the screen is equal to or greater than a        scanning angle of view, and    -   the third condition being that a numerical aperture of the        projection optical system on the screen side is 0.2 or greater.

The apparatus for measuring a scanning pattern of an optical scanningapparatus may further comprise a storage configured to store themeasured scanning pattern of the illumination light.

The apparatus for measuring a scanning pattern of an optical scanningapparatus may further comprise an image acquisition unit configured toimage the screen and acquire an image of the scanning pattern of theillumination light.

Another aspect of this disclosure is directed to a method forcalibrating an image in an optical scanning apparatus that calibratespixel positions of an image of an object being illuminated, the pixelpositions being obtained by scanning the object being illuminated withillumination light, and generates a display image of the object beingilluminated, the method comprising:

-   -   acquiring a scanning pattern of the illumination light before        scanning of the object being illuminated; and    -   generating the display image by calibrating pixel positions of        the image of the object being illuminated based on the scanning        pattern acquired in the step of acquiring a scanning pattern,        the pixel positions being obtained by scanning the object being        illuminated, wherein    -   the step of acquiring a scanning pattern comprises        -   scanning a screen with the illumination light; and        -   acquiring irradiation position information by sequentially            detecting, with an optical position detector, a position of            an irradiation spot of the illumination light on the screen            at a predetermined plurality of time points during scanning            of the screen.

The step of generating the display image may comprise:

-   -   acquiring pixel signals of the object being illuminated at a        predetermined plurality of time points during scanning of the        object being illuminated; and    -   arranging the pixel signals acquired in the step of acquiring        pixel signals at pixel positions corresponding to the        irradiation position information at the same time points as in        the step of acquiring irradiation position information.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram illustrating the main configuration of anapparatus for measuring a scanning pattern according to Embodiment 1;

FIG. 2 is a partially expanded cross-sectional diagram of the insertiontip of the optical scanning endoscope in FIG. 1;

FIG. 3 is a flowchart illustrating the main processing for scanningpattern measurement by the apparatus for measuring a scanning pattern inFIG. 1;

FIG. 4 illustrates the main configuration of an apparatus for measuringa scanning pattern according to Embodiment 2;

FIG. 5 illustrates the main configuration of an apparatus for measuringa scanning pattern according to Embodiment 3;

FIG. 6 illustrates the main configuration of an apparatus for measuringa scanning pattern according to Embodiment 4;

FIG. 7 is a block diagram schematically illustrating the mainconfiguration of an endoscopic observation apparatus according toEmbodiment 5; and

FIG. 8 is a flowchart illustrating the main processing of imagecalibration operations by the endoscopic observation apparatus in FIG.7.

DETAILED DESCRIPTION

If the optical scanning apparatus is, for example, a scanning endoscope,a large angle of view is required, such as 90°. In this case, theillumination light emitted from the scanning endoscope rapidly increasesa distance from the optical axis of the illumination optical system atthe scanning tip. On the other hand, the size of the light receivingsurface of a PSD, for example, is at most about 10 mm square. Directlymeasuring the scanning pattern of illumination light with a PSD,therefore, requires that the light receiving surface of the PSD beplaced within approximately 5 mm from the emission end face of thescanning endoscope.

Disposing the PSD near the emission end face of the scanning endoscope,however, gives rise to stray light due to multiple reflections betweenthe PSD and the emission end face in a state of high energy density.Such stray light causes the detection accuracy of the irradiationposition of illumination light to decrease. Consequently, themeasurement accuracy of the scanning pattern decreases with thecalibration method disclosed in PTL 1, leading to concerns over adecrease in image quality of the display image.

One possible method for decreasing such stray light is to dispose anoptical element, such as a wave plate or a polarizer, in front of thePSD. However, the PSD is provided with a cover glass or the like toprotect the light receiving surface, which further reduces the distancebetween the emission end face of the scanning endoscope and the PSD, andthat makes it difficult to dispose an optical element. Furthermore, anoptical element such as a wave plate or a polarizer exhibits incidenceangle dependence. Therefore, the ideal characteristics with respect toincident light cannot be obtained near an angle of view of 90° (an angleof incidence of 45°), and a reduction in the position detection accuracyis inevitable. This problem similarly occurs in other apparatuses, sucha laser scanning microscope that scans a sample through an objectivelens by deflecting laser light.

In light of these considerations, it would be helpful to provide amethod for measuring a scanning pattern of an optical scanningapparatus, an apparatus for measuring a scanning pattern, and a methodfor calibrating an image that can easily reduce the effect of straylight, improve the measurement accuracy of the scanning pattern, andachieve highly accurate image calibration.

Embodiments of this disclosure are described below with reference to thedrawings.

Embodiment 1

FIG. 1 is a block diagram illustrating the main configuration of anapparatus for measuring a scanning pattern according to Embodiment 1.The apparatus for measuring a scanning pattern according to thisembodiment is for measuring the scanning pattern of a scanning endoscope(scope) 100, mainly at the time of product shipment. The apparatus formeasuring a scanning pattern includes a measurement apparatus body 10, ascreen 11, and a PSD 12. As necessary, the measurement apparatus body 10includes a display 13 and an input interface 14, such as a keyboard, amouse, or a touch panel.

The scanning endoscope 100 is detachably connected to the measurementapparatus body 10 by a connector or the like. The screen 11 is mounteddirectly on the light receiving surface of the PSD 12 and is disposed atthe position scanned by illumination light emitted from the scanningendoscope 100. The screen 11 is preferably disposed at the position ofthe object being observed (object being illuminated) at the time ofendoscopic observation using the scanning endoscope 100. The screen 11also preferably has a thickness equal to or less than the spot diameterof the irradiated illumination light.

The PSD 12 outputs a detection signal corresponding to the irradiationposition of illumination light that passes through the screen 11 and isincident on the light receiving surface. The detection signal outputfrom the PSD 12 is input into the measurement apparatus body 10 througha signal wire 15.

An optical fiber 101 for illumination and optical fibers 102 forreceiving light (see FIG. 2) are disposed inside the scanning endoscope100 and extend from the base end joined to the measurement apparatusbody 10 to the insertion tip. Illumination light from the measurementapparatus body 10 can enter the optical fiber 101 for illumination whilethe scanning endoscope 100 is connected to the measurement apparatusbody 10.

As illustrated in the partially expanded cross-sectional diagram of FIG.2, an actuator 103 and an illumination optical system 104 are mounted inthe insertion tip of the scanning endoscope 100. The actuator 103includes a ferrule 110 as a fiber holder that holds an emission end 101a of the optical fiber 101 for illumination by the emission end 101 apassing through the ferrule 110. The optical fiber 101 for illuminationis adhered to the ferrule 110. The end of the ferrule 110 opposite froman emission end face 101 b of the optical fiber 101 for illumination isjoined to a support 105 so that the ferrule 110 is supported at one endby the support 105 to allow oscillation. The optical fiber 101 forillumination extends through the support 105.

The ferrule 110 is, for example, made of a metal such as nickel. Theferrule 110 may be formed in any shape, such as a quadrangular prism ora cylinder. Piezoelectric elements 106 x and 106 y are mounted on theferrule 110 to oppose each other in the x-direction and the y-direction,where the x-direction and y-direction are orthogonal to each other in aplane orthogonal to the z-direction, and the z-direction is a directionparallel to the optical axis direction of the optical fiber 101 forillumination. Only one of the piezoelectric elements 106 x isillustrated in FIG. 2. The piezoelectric elements 106 x and 106 y arerectangular, with the long sides in the z-direction. The piezoelectricelements 106 x and 106 y each have an electrode formed on both surfacesin the thickness direction and are each configured to be capable ofexpanding and contracting in the z-direction upon voltage being appliedin the thickness direction via the opposing electrodes.

Corresponding wiring cables 107 are connected to the electrode surfacesof the piezoelectric elements 106 x and 106 y opposite the electrodesurfaces adhered to the ferrule 110. Similarly, corresponding wiringcables 107 are connected to the ferrule 110, which acts as a commonelectrode for the piezoelectric elements 106 x and 106 y. To the twopiezoelectric elements 106 x opposite each other in the x-direction,in-phase AC voltage is applied from the measurement apparatus body 10through the corresponding wiring cables 107. Similarly, to the twopiezoelectric elements 106 y opposite each other in the y-direction,in-phase AC voltage is applied from the measurement apparatus body 10through the corresponding wiring cables 107.

With this configuration, when one of the two piezoelectric elements 106x expands, the other contracts, causing the ferrule 110 to vibrate bybending in the x-direction. Similarly, when one of the two piezoelectricelements 106 y expands, the other contracts, causing the ferrule 110 tovibrate by bending in the y-direction. As a result, the x-directionvibration and y-direction vibration are combined, so that the ferrule110 is deflected integrally with the emission end 101 a of the opticalfiber 101 for illumination. Accordingly, upon illumination lightentering the optical fiber 101 for illumination from the measurementapparatus body 10, the illumination light emitted from the emission endface 101 b is deflected in two dimensions.

The optical fibers 102 for receiving light are disposed as a bundle atthe outer circumferential portion of the scanning endoscope 100. Anon-illustrated detection lens may also be disposed at the entrance tip102 a side of the optical fibers 102 for receiving light. While thescanning endoscope 100 is connected to the observation apparatus bodyfor endoscopic observation, reflected light, fluorescent light, or otherlight is yielded by the object being observed (object being illuminated)as a result of irradiation with the illumination light from the opticalfiber 101 for illumination. The optical fibers 102 for receiving lightcapture this light as signal light and guide the signal light to theobservation apparatus body.

The example of the illumination optical system 104 in FIG. 2 isconfigured by two projection lenses 104 a, 104 b. The projection lenses104 a, 104 b are configured so as to concentrate illumination light,emitted from the emission end face 101 b of the optical fiber 101 forillumination, on a predetermined focal position. The illuminationoptical system 104 is not limited to two projection lenses 104 a, 104 band may be configured as a single lens or as three or more lenses.

As illustrated in FIG. 1, the scanning endoscope 100 further includes astorage 108. Scanning pattern information on the illumination light fromthe optical fiber 101 for illumination when the actuator 103 of thescanning endoscope 100 is driven with a predetermined drive signal isstored in the storage 108. During endoscopic observation using thescanning endoscope 100, the scanning pattern information stored in thestorage 108 is read by the observation apparatus body while the scanningendoscope 100 is connected to the observation apparatus body.

The measurement apparatus body 10 in FIG. 1 includes a controller 16that controls operations of the apparatus overall, a light source 17, adrive controller 18, a calculator 19, and a storage 20.

The light source 17 includes a light source such as a laser diode or aDiode-Pumped Solid-State (DPSS) laser. As during endoscopic observationof color images with the scanning endoscope 100, the light source 17 maybe configured with a plurality of lasers that emit blue, green, and redlaser light, or the light source 17 may be configured with a singlelaser for scanning pattern measurement. Light emitted from the lightsource 17 is incident on the optical fiber 101 for illumination of thescanning endoscope 100.

The drive controller 18 supplies the actuator 103 of the scanningendoscope 100 with a predetermined drive signal, over the wiring cables107, that is similar to the drive signal for scanning the target area ofthe object being observed during endoscopic observation, and vibratesthe emission end 101 a of the optical fiber 101 for illumination. Inthis embodiment, the actuator 103 includes the piezoelectric elements106 x and 106 y. As drive signals, the drive controller 18 thus appliesvoltage that gradually increases and then decreases in amplitude to thepiezoelectric elements 106 x and 106 y. The drive signals differ inphase by nearly 90° and are at or near the resonance frequency of thevibrated portion, which for example includes the emission end 101 a ofthe optical fiber 101 for illumination. As a result, the emission endface 101 b of the optical fiber 101 for illumination is displaced in aspiral shape centered on the optical axis of the illumination opticalsystem 104, and the screen 11 is scanned in a spiral shape by theillumination light emitted from the emission end face 101 b.

The calculator 19 receives input of the detection signal output by thePSD 12 and converts the detection signal into coordinates (x, y) at asequential predetermined plurality of time points t_(k) (k=0, 1, . . . ,n) from the start of scanning of the screen 11 by the illuminationlight. As a result, the calculator 19 captures the position of theirradiation spot on the screen 11 at sequential predetermined timepoints from the start of scanning of the screen 11 by the illuminationlight. The calculator 19 may smooth the error in the coordinate positionof the illumination spot as necessary using a method such as polynomialapproximation. The result of calculation by the calculator 19, i.e. theirradiation position information associated with the elapsed time of thescan, is stored in the storage 20. Upon the irradiation positioninformation over one scan being stored in the storage 20, the controller16 stores the irradiation position information as scanning patterninformation in the storage 108 of the scanning endoscope 100.

The storage 20 stores information such as control programs of themeasurement apparatus body 10. The storage 20 also functions as aworking memory of the calculator 19, as described above. The storage 20may be an internal memory of the measurement apparatus body 10 or may bea portable storage medium (such as a memory card) removable from themeasurement apparatus body 10.

FIG. 3 is a flowchart illustrating the main processing for scanningpattern measurement of the scanning endoscope 100 by the apparatus formeasuring a scanning pattern according to this embodiment. To preparefor measurement, the scanning endoscope 100 to be measured is connectedto the measurement apparatus body 10, and the PSD 12 with the screen 11mounted thereon is disposed facing the emission end of the scanningendoscope 100. In this state, the controller 16 drives the light source17, and the drive controller 18 drives the actuator 103 of the scanningendoscope 100 to start scanning of the screen 11 with illumination light(step S301).

Next, during scanning of the screen 11, the controller 16 uses thecalculator 19 to convert the detection signal input from the PSD 12 intocoordinates (x, y) at a sequential predetermined plurality of timepoints t_(k) (k=0, 1, . . . , n) from the start to the end of scanning.By doing so, the controller 16 captures the sequential position of theirradiation spot on the screen 11 with the calculator 19, therebyacquiring the irradiation position information (step S302). Thisirradiation position information is associated with the elapsed time ofthe scan and stored in the storage 20.

Subsequently, upon the irradiation position information over one scanbeing stored in the storage 20, the controller 16 ends the scanning ofthe screen 11, stores the irradiation position information over onescan, which was stored in the storage 20, in the storage 108 of thescanning endoscope 100 as scanning pattern information (step S303), andends the scanning pattern measurement operation of the scanningendoscope 100.

In the flowchart illustrated in FIG. 3, step S301 corresponds to a stepof scanning a screen, and step S302 corresponds to a step of acquiringirradiation position information. Processing that includes steps S301 toS303 corresponds to a step of acquiring a scanning pattern.

The apparatus for measuring a scanning pattern according to thisembodiment uses illumination light irradiated from the scanningendoscope 100 to be measured in order to scan the screen 11, which ismounted directly on the light receiving surface of the PSD 12. Theillumination light incident on the screen 11 is then scattered by thescreen 11, and a portion of the scattered light passing through thescreen 11 is incident on the light receiving surface of the PSD 12.

Among the light scattered by the screen 11, light that returns in thedirection of the scanning endoscope 100 (backscattered light) is highlyscattered. A portion of this scattered light is reflected by thescanning endoscope 100 and is incident again on the screen 11. The lightthat is incident again on the screen 11 is then scattered once again bythe screen 11. Hence, the light that passes through the screen 11 to beincident on the PSD 12 is extremely weak. The effect of stray lightincident on the PSD 12 because of multiple reflections between thescreen 11 and the scanning endoscope 100 can therefore easily bereduced, allowing improvement in the measurement accuracy of thescanning pattern. Furthermore, by setting the thickness of the screen 11to be equal to or less than the diameter of the irradiation spot ofillumination light incident on the screen 11, the extent to which theirradiation spot incident on the PSD 12 is blurred can be reduced,thereby further improving the scanning pattern measurement accuracy.

Embodiment 2

FIG. 4 illustrates the main configuration of an apparatus for measuringa scanning pattern according to Embodiment 2. The apparatus formeasuring a scanning pattern according to this embodiment differs fromthe scanning pattern measurement apparatus in FIG. 1 in the arrangementof the PSD 12. FIG. 4 illustrates only the portion of the configurationthat differs from FIG. 1. The differences in configuration from FIG. 1are described below.

As is clear from FIG. 4, the apparatus for measuring a scanning patternaccording to this embodiment causes a portion of the backscattered lightoccurring at the screen 11 to be incident on the PSD 12 through aprojection optical system 21. The light receiving surface of the PSD 12is disposed at a position conjugate with the screen 11 with respect tothe projection optical system 21. As a result, the projection opticalsystem 21 projects the irradiation spot of illumination light incidenton the screen 11 onto the light receiving surface of the PSD 12,allowing measurement of the scanning pattern of the illumination light.In this embodiment, the screen 11 is preferably configured so that thediffusion angle of the illumination light is equal to or greater thanthe scanning angle of view. The projection optical system 21 ispreferably configured to have a numerical aperture on the screen 11 sideof 0.2 or greater.

In this way, the projection optical system 21 projects the irradiationspot on the screen 11 onto the PSD 12 with backscattered light from thescreen 11, allowing measurement of the scanning pattern of theillumination light in this embodiment. Among the light scattered at thescreen 11, the backscattered light is highly scattered. A portion ofthis scattered light is reflected by the scanning endoscope 100 and isincident again on the screen 11. The light that is incident again on thescreen 11 is then scattered once again by the screen 11. Hence, even ifa portion of that backscattered light is incident on the PSD 12 throughthe projection optical system 21, the light is extremely weak. As inEmbodiment 1, the effect of stray light incident on the PSD 12 becauseof multiple reflections between the screen 11 and the scanning endoscope100 can therefore easily be reduced, allowing improvement in themeasurement accuracy of the scanning pattern.

As in Embodiment 1, by setting the thickness of the screen 11 to beequal to or less than the diameter of the irradiation spot ofillumination light incident on the screen 11, the extent to which theirradiation spot incident on the PSD 12 is blurred can be reduced inthis embodiment as well, thereby further improving the scanning patternmeasurement accuracy. Also, by setting the diffusion angle of theillumination light by the screen 11 to be equal to or greater than thescanning angle of view, the proportion of the backscattered light thatis collected by the projection optical system 21 can be increased. Theamount of light incident on the PSD 12 can therefore be increased,further improving the scanning pattern measurement accuracy. Similarly,by setting the numerical aperture of the projection optical system 21 onthe screen 11 side to be 0.2 or greater, a greater amount ofbackscattered light can be collected, allowing an increase in the amountof light incident on the PSD 12 and further improving the scanningpattern measurement accuracy.

Embodiment 3

FIG. 5 illustrates the main configuration of an apparatus for measuringa scanning pattern according to Embodiment 3. The apparatus formeasuring a scanning pattern according to this embodiment differs fromthe apparatus for measuring a scanning pattern in FIG. 4 in thearrangement of the PSD 12. FIG. 5 illustrates only the portion of theconfiguration that differs from FIG. 4. The differences in configurationfrom FIG. 4 are described below.

As is clear from FIG. 5, the apparatus for measuring a scanning patternaccording to this embodiment causes a portion of the forward-scatteredlight occurring at the screen 11 to be incident on the PSD 12 through aprojection optical system 21. The projection optical system 21 forexample includes two relay lenses 21 a and 21 b. The light receivingsurface of the PSD 12 is disposed at a position conjugate with thescreen 11 with respect to the projection optical system 21. As a result,the projection optical system 21 projects the irradiation spot ofillumination light incident on the screen 11 onto the light receivingsurface of the PSD 12, allowing measurement of the scanning pattern ofthe illumination light.

In this way, the projection optical system 21 projects the irradiationspot on the screen 11 onto the PSD 12 with forward-scattered light fromthe screen 11, allowing measurement of the scanning pattern of theillumination light in this embodiment. Among the light scattered at thescreen 11, the backscattered light is highly scattered. A portion ofthis scattered light is reflected by the scanning endoscope 100 and isincident again on the screen 11. The light that is incident again on thescreen 11 is then scattered once again by the screen 11. Hence, even ifa portion of the forward-scattered light is incident on the PSD 12through the projection optical system 21, the light is extremely weak.As in Embodiment 1, the effect of stray light incident on the PSD 12because of multiple reflections between the screen 11 and the scanningendoscope 100 can therefore easily be reduced, allowing improvement inthe measurement accuracy of the scanning pattern.

In this embodiment as well, as in Embodiment 2, satisfying at least oneof the following conditions further improves the scanning patternmeasurement accuracy. Condition 1: the thickness of the screen 11 is setto be equal to or less than the diameter of the irradiation spot ofillumination light incident on the screen 11. Condition 2: the diffusionangle of the illumination light by the screen 11 is set to be equal toor greater than the scanning angle of view. Condition 3: the numericalaperture of the projection optical system 21 on the screen 11 side isset to be 0.2 or greater.

Embodiment 4

FIG. 6 illustrates the main configuration of an apparatus for measuringa scanning pattern according to Embodiment 4. The apparatus formeasuring a scanning pattern according to Embodiment 4 has theconfiguration of the apparatus for measuring a scanning patternillustrated in FIG. 5, with the addition of a beam splitter 22, an imageforming optical system 23, and an imager 24. FIG. 6 illustrates only theportion of the configuration that differs from FIG. 5. The differencesin configuration from FIG. 5 are described below.

The beam splitter 22 is, for example, composed of a half-mirror placedon the optical axis between the two relay lenses 21 a and 21 bconstituting the projection optical system 21. The beam splitter 22reflects a portion of the light traveling towards the relay lens 21 b.The image forming optical system 23 forms an image on the imager 24 withlight reflected by the beam splitter 22. The imager 24 is configured toinclude a CCD or other such device, the output of which for example issubjected to image processing by the measurement apparatus body 10 inFIG. 1 and is displayed on the display 13.

This embodiment not only achieves the effects of Embodiment 3 but alsoallows the scanning pattern of the scanning endoscope 100 to be observedas an image. A good judgement of the scanning pattern can thus, forexample, be made visually.

Next, an embodiment of an endoscopic observation apparatus that uses thescanning endoscope 100 for which the scanning pattern has been measuredas described in Embodiments 1 to 4 is described.

Embodiment 5

FIG. 7 is a block diagram schematically illustrating the mainconfiguration of an endoscopic observation apparatus according toEmbodiment 5. An endoscopic observation apparatus 30 illustrated in FIG.7 includes an observation apparatus body 40, a display 60, and ascanning endoscope 100.

The scanning endoscope 100 is detachably connected to the observationapparatus body 40 by a connector or the like. The observation apparatusbody 40 includes a controller 41 that controls the entire endoscopicobservation apparatus 30, a light source 42, a drive controller 43, anoptical detector 44, an image processor 45, and a storage 46.

The light source 42 includes lasers 51R, 51G, 51B and a multiplexer 52.The laser 51R emits red laser light, the laser 51G emits green laserlight, and the laser 51B emits blue laser light. For example,Diode-Pumped Solid-State (DPSS) lasers or laser diodes may be used asthe lasers 51R, 51G, and 51B. The wavelength of each color of light may,for example, be from 440 nm to 460 nm for blue, 515 nm to 532 nm forgreen, and 635 nm to 638 nm for red. The laser light emitted from thelasers 51R, 51G, and 51B is combined on the same axis by the multiplexer52 and is incident on the optical fiber 101 for illumination of thescanning endoscope 100. The light source 42 may include a differentplurality of light sources. The light source 42 may also be stored in ahousing that is separate from the observation apparatus body 40 and isconnected to the observation apparatus body 40 by a signal wire. In thiscase, the optical fiber 101 for illumination of the scanning endoscope100 is detachably connected to the housing that includes the lightsource 42.

The drive controller 43 supplies the actuator 103 of the scanningendoscope 100 with a required drive signal, over the wiring cables 107,for scanning the target area of the object being observed 70 andvibrates the emission end 101 a of the optical fiber 101 forillumination. The required drive signal is the same drive signal as whenmeasuring the scanning pattern of the scanning endoscope 100. Forexample, as drive signals, the drive controller 43 applies voltage thatgradually increases and then decreases in amplitude to the piezoelectricelements 106 x and 106 y. The drive signals differ in phase by nearly90° and are at or near the resonance frequency of the vibrated portion,which includes the emission end 101 a of the optical fiber 101 forillumination. As a result, the emission end face 101 b of the opticalfiber 101 for illumination is displaced in a spiral shape centered onthe optical axis of the illumination optical system 104, and the targetarea of the object being observed 70 is scanned in a spiral shape by theillumination light emitted from the emission end face 101 b.

The optical detector 44 includes a spectrometer 55, photodetectors (PDs)56R, 56G, 56B, and Analog-Digital Converters (ADCs) 57R, 57G, 57B. Whilethe scanning endoscope 100 is connected to the observation apparatusbody 40, the spectrometer 55 is connected to the optical fibers 102 forreceiving light of the scanning endoscope 100. The signal light guidedby the optical fibers 102 for receiving light is divided for exampleinto the colors R, G, B. The PDs 56R, 56G, 56B detect the light of thecorresponding color split by the spectrometer 55 and subject the lightto photoelectric conversion. The PDs 56R, 56G, 56B then output analogpixel signals, which the corresponding ADCs 57R, 57G, 57B sample atpredetermined timings, convert to digital pixel signals, and output tothe image processor 45.

While the scanning endoscope 100 is connected to the observationapparatus body 40, the image processor 45 reads the scanning patterninformation of the scanning endoscope 100 from the storage 108. Theimage processor 45 then stores the pixel signals for each color,obtained from the ADCs 57R, 57G, 57B during scanning of the object beingobserved 70, at rendering positions of a frame memory in correspondencewith the time points in the scanning pattern information read from thestorage 108. The image processor 45 thus calibrates the pixel positionsof pixel signals of each color obtained from the ADCs 57R, 57G, 57B byreferring to the scanning pattern information read from the storage 108and stores the pixel positions at the corresponding rendering positionsin the frame memory. The image processor 45 performs necessary imageprocessing, such as interpolation, during or after the completion ofscanning of each frame, generates images of sequential frames of theobject being observed 70, and displays the images on the display 60.

The storage 46 stores information such as control programs of theobservation apparatus body 40. The storage 46 may also function as aworking memory for the image processor 45.

FIG. 8 is a flowchart illustrating the main processing of imagecalibration operations performed by the endoscopic observation apparatus30 in FIG. 7. First, the controller 41 drives the light source 42 andthe drive controller 43 drives the actuator 103 of the scanningendoscope 100 to start scanning of the object being observed 70 withillumination light (step S801).

Next, during scanning of the object being observed 70, the controller 41uses the optical detector 44 to sample analog pixel signals, output fromthe PDs 56R, 56G, 56B, with the ADCs 57R, 57G, 57B at a sequentialpredetermined plurality of time points t_(k) (k=0, 1, . . . , n) fromthe start of scanning to acquire digital pixel signals (step S802).

Subsequently, the controller 41 uses the image processor 45 to performimage calibration by storing pixel signals of each color obtained fromthe ADCs 57R, 57G, 57B at rendering positions of the frame memory incorrespondence with the time points in the scanning pattern informationread from the storage 108 (step S803). The controller 41 then uses theimage processor 45 to perform necessary image processing, such asinterpolation, based on the calibrated pixel signals at the renderingpositions, to generate an image of the object being observed 70 and todisplay the image on the display 60 (step S804).

In the flowchart in FIG. 8, steps S801 and S802 correspond to the stepof generating the pixel signals, and step S803 corresponds to a step ofarranging the pixel signals. Processing that includes steps S801 to S803corresponds to a step of generating a display image.

The endoscopic observation apparatus 30 according to this embodimentthus calibrates the pixel positions of the object being observed 70using the scanning pattern information measured through the screen asthe scanning pattern information of the scanning endoscope 100 in use.This configuration allows highly accurate image calibration and yields ahigh quality observation image.

This disclosure is not limited to the above embodiments, and a varietyof changes or modifications may be made. For example, in Embodiment 5,the observation apparatus body 40 may include the functions of themeasurement apparatus body 10 in FIG. 1, and as described in Embodiments1 to 4, before scanning the object being observed 70, the PSD 12 may beconnected, and the observation apparatus body 40 may measure thescanning pattern of the scanning endoscope 100 through the screen 11,subsequently calibrate the scanning image of the object being observed70, and display the image. In this case, the measured scanning patterninformation may be stored in the storage 46 of the observation apparatusbody 40, and the storage 108 of the scanning endoscope 100 may beomitted. Also, the scanning pattern information may be measured as abovefor various types of scanning endoscopes 100, and the various pieces ofscanning pattern information may each be stored along withidentification information on the corresponding scanning endoscope 100in the storage 46 of the observation apparatus body 40, and theidentification information of a scanning endoscope 100 may be stored inthe storage 108 of the scanning endoscope 100. The scanning patterninformation for the identification information corresponding to thescanning endoscope 100 connected to the observation apparatus body 40may then be read, and image calibration of the object being observed 70may be performed.

If the time points at which the position of the irradiation spot(coordinate information) is acquired are the same as the time points atwhich the pixel signals of the object being observed 70 are acquired,the scanning pattern information may be chronological coordinateinformation, omitting the time information. The image of the objectbeing observed 70 may be calibrated by temporarily storing the scanningimage of the object being observed 70 in memory and then rearranging thepixel positions based on the scanning pattern information.

In FIG. 1, a portion or the entirety of the drive controller 18,calculator 19, and storage 20 may be included in the controller 16.Similarly, in FIG. 7, a portion or the entirety of the drive controller43, the optical detector 44, the image processor 45, and the storage 46may be included in the controller 41. The actuator 103 of the scanningendoscope 100 is not limited to a piezoelectric method and may insteadadopt another known driving method, such as a MEMS mirror or anelectromagnetic method that uses coils and a permanent magnet. InEmbodiment 5, the case of scanning by simultaneously irradiating lightof the colors R, G, B on the object being observed 70 has beendescribed. Alternatively, light of each color may be irradiated andimages displayed by a frame sequential method, or light of each colormay be irradiated sequentially within one scan, with an image then beingdisplayed. Furthermore, this disclosure is not limited to an endoscopicobservation apparatus and may also be adopted in a scanning microscope.

REFERENCE SIGNS LIST

10 Measurement apparatus body

11 Screen

12 PSD (optical position detector)

16 Controller

17 Light source

18 Drive controller

19 Calculator

20 Storage

21 Projection optical system

22 Beam splitter

23 Image forming optical system

24 Imager

30 Endoscopic observation apparatus

40 Observation apparatus body

41 Controller

42 Light source

43 Drive controller

44 Optical detector

45 Image processor

46 Storage

100 Scanning endoscope

101 Optical fiber for illumination

102 Optical fibers for receiving light

103 Actuator

104 Illumination optical system

108 Storage

The invention claimed is:
 1. An apparatus for calibrating an opticalscanning apparatus that scans an object being illuminated withillumination light and generates a display image of the object beingilluminated, the apparatus comprising: a screen arranged to be scannedby the illumination light; an optical position detector configured todetect irradiation spots of the illumination light on the screen; aprojection optical system configured to project the irradiation spots onthe screen onto the optical position detector; and a processorconfigured to sequentially detect positions of the irradiation spots ata predetermined plurality of time points to measure a scanning patternof the illumination light.
 2. The apparatus according to claim 1,wherein the screen has a thickness equal to or less than a diameter ofone of the irradiation spots.
 3. The apparatus according to claim 1,wherein at least one of a first condition, a second condition, and athird condition is satisfied: the first condition being that the screenhas a thickness equal to or less than a diameter of one of theirradiation spots; the second condition being that a diffusion angle ofthe illumination light by the screen is equal to or greater than ascanning angle of view; and the third condition being that a numericalaperture of the projection optical system on the screen side is 0.2 orgreater.
 4. The apparatus according to claim 1, further comprising astorage configured to store the measured scanning pattern of theillumination light.
 5. The apparatus according to claim 1, furthercomprising an image sensor configured to image the screen and acquire animage of the scanning pattern of the illumination light.